Black outs, frequent brown outs, wastage of power and deterioration in power line quality are major problems in the electrical power distribution system of developing countries. Usage of PCs is increasing in the urban and suburban region exponentially in domestic, commercial and industrial sectors which calls for a proportional increase in the use of UPS systems to take care of the unreliable utility power conditions. A significant amount of money is to be spent for the procurement and maintenance of the UPS systems. Uncontrolled increase of online UPS systems results in high level of harmonics induction in to power lines. Power consumed by UPS depends on the quality of design and components used which will directly add to the wasted power. Many of the products popular in the market including branded ones produce current and voltage surges, distorted wave forms and other deteriorations in the power line quality. Wastage of costly floor space for placing UPS and battery is another important concern. Chances of fire hazards due to capacitor banks, high power switching inside UPS and discharges from batteries are other difficulties faced. Low overall efficiency, poor power factor and comparatively lower reliability are other limitations. Another concern is about the efficiency of the conventional SMPS used internally to power PCs and other equipments. The popular brands commercially available in desktop PCs in the market were tested for its overall efficiency and the result was as low as 35% when used along with online UPS systems.
Generally UPSs are classified as on line and off line categories. Off line category has very low KVA rating. Online UPS is expensive and requires frequent maintenance. It also generates more harmonics and cause related grounding issues. In addition to online and offline, line interactive (Mains and inverter power synchronized) models are also available which are not generally recommended for PC applications. Mains supply is converted in to DC and then to AC inside UPS. This AC from UPS is again converted to required DC voltages in the PC. This multistage AC/DC and DC/AC conversions in UPS and SMPS make system low efficient and increases the chances of breakdown. Due to low overall efficiency of PC SMPS with UPS combination, backup time is very low considering the actual mother board power requirement.
An extensive prior art search has been conducted which revealed the existence of following devices which are currently in use for the above mentioned applications.
Three major brands of UPS for PC application were compared for their performance through power in watts (W), volt ampere (VA), reactive power (VAR), power factor (PF) and input current (I).
UPS MODELNO LOADONE PCTWO PCTHREE PCDELTAW = 49W = 106W = 165W = 223MODEL 1 KVAVA = 100VA = 133VA = 185VA = 240GES102N212035VAR = −85VAR = −75VAR = −85VAR = −100S NO 82L10600451WKV = 229V = 229V = 229V = 229I = 0.43I = 0.52I = 0.81 = 1.05PF = 0.45leadPF = 0.8leadPF = 0.88leadPF = 0.94leadEATON E SERIES DXW = 56W = 118W = 170W = 234MODEL 1 KVA/0.8 KWVA = 93VA = 134VA = 190VA = 248S NO 130109-25100179VAR = −69VAR = −70VAR = −71VAR = −68V = 229V = 229V = 229V = 229I = 0.40I = 0.59I = 0.83I = 1.07PF = 0.62leadPF = 0.85leadPF = 0.936leadPF = 0.96leadEATON E SERIES DXW-56W = 145W = 216W = 228MODEL 1 KVA/0.8 KWVA = 93VA = 163VA = 223VA = 292S NO 130109-25100179VAR = −69VAR = −68VAR = −65VAR = −63(CPU LOADED)V = 229V = 229V = 229V = 229I = 0.4I = 0.71I = 0.98I = 1.3PF = 0.62leadPF = 0.90leadPF = 0.96leadPF = 0.98leadAPC 550 VAW = 9W = 72W = 127W = 190MODEL RS 550VA = 27VA = 145VA = 249VA = 312S NO BB0947021887VAR = −26VAR = −125VAR = −211VAR = −244V = 229V = 229V = 229V = 229I = 0.11I = 0.6I = 1.08I = 1.32PF = 0.32leadPF = 0.49leadPF = 0.522leadPF = 0.58lead
The conventional SMPS used as power supply in PC has no power backup capability, it cannot accept solar panel output directly and causes more power loss resulting in poorer efficiency.
To sum up, the existing devices are providing only lower efficiency, economy and reliability. The above drawbacks of the prior art evolved a need for development of a new device which supports any gadget requiring steady and clean input DC power with an extended back up facility.